Improvement in operating-valves for steam-engines



2 Sheet s---Sheet I.

T. H. MITCHELL. Improvement in Operating Valves for Steam-Engines. N0. 130,654. Patented Aug 20,1872.

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2Sheets--Sheet2. T. H. MITCHELL.

Patented Aug. 20, 1872.

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WITNESSES:

INVENTOB:

IMPIlDTJ-L/Ff/UCRAFHIG' C0 MX/VSEONI'I'ES' PHJCESS UN TED STATEs THOMAS H. MITCHELL, OF ALBANY, rnw YORK.

IMPROVEMENT IN OPERATING-VALVES FOR STEAM-ENGINES.

Specification forming part of Letters Patent No. 130,654, dated August 20, 1872.

SPEOIFIOATION.

. To all whom it may concern:

Be it known that I, THOMAs H. MITCHELL, of Albany, in the county of Albany, in the State of New York, have invented new and useful Improvements in Steam-Engines; and I do hereby declare that the followingis a full and exact description thereof, reference being had to the accompanying drawing and to the letters of reference marked thereon making a part of this specification.

To enable others skilled in the art to make and use myinvention, I will proceed to describe its construction and operation.

The drawing represents a horizontal engine.

Figure 1 is a top view of the engine. Fig. 2 is a side view of engine, partly in section. Fig. 3 is the opposite-side view of engine. Fig. 4 is a horizontal sectional view of post B and eccentric pin n. Fig. 5 is a view of rocking plate. Fig. 6 is a view of rocking plate and notched wheel. Fig. 7 is aview of the halved cams with links attached. Fig. 8 is a view of the slotted adjuster P. Fig. 9 is a horizontal sectional view of post B and rock-shaft c and connections, as described.

. A A is the bed-plate. O is the cylinder. D is the steam-chest. E is the piston. F F are the cylinder-heads. H is the cross-head. K is the crank-plate. L is the pillow-block. M is the main valve-rod. O is the eccentric flange. P is the slotted adjuster. U U are the halved cams. a is thepiston-rod. b is the main valve. 0 is the exhaust-port. c is the rock-shaft. cl is the arm keyed to the rock-shaft e. j is the screw which connects the valve-rod M to the arm d. I is the main rod connecting the crosshead H with the crank-pin g of plate K. o is the screw-joint in cross-head H. ff are the guides to cross-head H. Z is the engine-shaft.

Fig. 2 shows a perpendicular section of steamcylinder 0 and steam-chest D. N is the rod connecting the eccentric pin 3 of eccentric plate 0 to rocking plate 8 at joint 3. o o are pawls, having fulcrums passing through rocking plate s, as also shown in Fig. 5 by 7 7 w 'w is a spring, for the purpose of forcing the pawls c t o t against the notched wheel a and half-cams a a. This spring is fastened to rockin g plates at screw-joint V. T is a square box, fitting loose on rock-shaft e. 1 is a hook fastened into rod Z, attaching spring .9 to it. 8 8

are links connecting the adjuster P with the halved cams U U at joints 5 5 andet 4. X is the permanent guide to rod 11 of adjuster P. n is a permanent shaft fastened into post B on which the eccentric 7' plays. 12 is the eccentric strap of eccentric r, and is connected by rod 11 of adjuster P by screw-pin 2. h is the pin to which an engine-governor may be attached. The lever 15, to which the pin h is attached, is firmly fastened to the eccentric r. a is a wheel with a section of the periphery cut away forming two shoulders, against which the two pawlst t play. lis arod, in'which the pin i is fastened, and the opposite end of rod 1 is attached to the notched wheel a by the screw-pin 13, as also shown in Fig. 6. m m It It are the highest points of the four inclined planes, and terminate at the lowest point p. S is the spring attached to the hook 1 and screw 10, which'is screwed into bed-plate A A. The arrow on the crank-plate K' shows the direction the crank should move. The arrows in the steam-chest D and cylinder 0 show the direction vwhich the steam. takes as it'enters the inlet 9. j

The operation of the engine is as follows The steam passes through the inlet 9, taking the direction of the arrows of steam-chest D and cylinder 0, a'sshown in Fig. 2, pressing against piston E, and is exhausting on theop'e;

posite side of piston E through port-l2; and so on, out of the exhaust-port 0; and as soon as the piston has reached one-fourth of the length of its stroke all communication is closed from the steam-chest D and exhaust-port 0, the piston E traveling the remainder of the stroke by the expansion of the steam, which it has received from the steam-chest D. The broken lines in steam-chest D show the main valve 1) when in position to close the ports, as before described. The steam on the exhaust side of piston E having exhausted, and the main valve being closed over the three ports, there is a vacuum which inclines the exhaust side of the piston toward cylinder-head F, shown in Fig. 2. A vacuum takes places after the steam is exhausted and is retained by the closing of the main valve b. Pin 71. may be controlled by hand or a governor when attached to it. When pin it is in the position as seen in the drawing, the apparatus, which is controlled by this pin, trips the pawls o to e X I 130,654

as the adjuster P is connected by links 8 8 to the half cams U U, these cams are controlled by moving the pin h toward h, the distance between 12 12 of cams U U is shortened, and

' thus cuts oil the steam shorter, and by moving the pin h in the opposite direction it lengthens the cut-off. Spring w w presses the pawls 'v t against the half cams, shown in part by broken lines of Fig. 3, and in full by Fig. 7, and also against the notched wheel a, as in Fig. 6. The four pawls o t and o 15, Figs. 5 and 6, have two pins, 7 7, which pass through the rocking plate, and are keyed into the pawls at the extremities of the pins; thus the pawls work inpairs, each pair moving in unison. The rocking plate 8 of Fig. 3 is moved by be- 7 ing connected to the eccentric pin y by means of the rod N; thus the rocking plate s moves uniformly with the eccentric, not connected to the rock-shaft except through the working of the pawls t t moving in and out of notches 16 16, of wheel a, as shown in Fig. 6. The pin t of rod Z, having reached the point it now 00- cnpies on the inclined plane k, as shown by letters k k of Fig. 1, the piston E is supposed to have reached one-fourth the length of its stroke, the pawl o strikes the half cam U at point 12, and, being connected with the pawl t, it rises out from against the shoulder 16 of notched flange u. The spiral spring S being attached to the connecting-rod l by means of hook 1, the pin t passing through rod 1, resting on the inclined planes at It It, said spring S inclines the pin 11 back to its former position at p. The pawl it, being thrown out from against the notch at 16, the pin 'i returns to its position at 12. When the notched flange u moves in the opposite direction-from the arrow of flange to its motion corresponds with that of pin "6, being connected by rod 1. Now, as the notched flange u returns pawl t drops into the other notch 16, and the same motion is repeated after the crank-pin g has made half of a revolution in the direction of the arrow on crank-plate K. The, notched flange a is keyed to the rock-shaft e, as is also the arm d. The main valve 1) is connected with the valve-rod M, being also connected at screwjoint j with the arm (I; thus the main valve may be controlled by hand, or regulated by a governor, when connected with the pin h. The four inclined planes k k m mmeet at p of Fig. 3, corresponding with the broken lines in steam-chest D, showing the main valve b as covering the ports having lap enough over the width of each of the three ports, so as to cover them steam-tight; thus there is no communication between the cylinder 0, steamchest D, or exhaust-port c of Fig. 2 thus the vacuum becomes serviceable.

It will be perceived, by means of the apparatus herein described, that theregular revolutions of the engine-shaft z is controlled by handor a governor. The main valve 12, when in the position of the broken lines, cuts off the steam and closes the exhaust-port 0, thus securing the vacuum and assisting the motion of the piston E. An oscillating valve may be used instead of a flat valve for the main valve.

It will also be perceived that when the pin h is moved in the direction of the dotted arc to h, the motion of the main valve ceasing serves as a throttle, closing off the head of steam from the cylinder 0, and when pin h is at h the steam-cylinder receives the full head of steam. 1

Having thus described my invention, what Iclaim, and desire to secure by Letters Patent, 1s-

The combination of the rocking plate 8, pawls o t o t, guide 00, rod 11, links 8 8, cams U U, notched wheel 10, adjusted by the running gear of a governor, or by hand, with inclined planes m k, pin t, and spring S, all arranged to operate the valve I), substantially as set forth.

THOMAS H. MITCHELL.

Witnesses:

THOMAS MITCHELL, AMANDA H. MITCHELL. 

